1. Field of the Invention
The present invention relates to an image forming apparatus, a method of controlling the same, a program, and an image forming system.
2. Description of the Related Art
An image forming apparatus is recently required to not only reduce the cost and size but also achieve greater functionality. A technique is known to meet these requirements, which causes an image forming apparatus and an external apparatus to cooperatively perform information processing so as to provide maximum functions and performance using limited hardware resource. This technique causes an image forming apparatus and an external apparatus (for example, a server or a PC) to cooperatively execute information processing and image processing, thereby implementing an extension function (for example, extension copy function) that cannot be provided by the hardware resource of the image forming apparatus.
For example, Japanese Patent Laid-Open No. 08-186677 proposes a technique which connects an image forming apparatus to an external apparatus such as a personal computer (to be referred to as a PC hereinafter), and causes the PC to process an image obtained by the image forming apparatus. In this publication, the PC executes image processing, which is executed by the image forming apparatus in the conventional copy function, thereby reducing use of the hardware resource of the image forming apparatus. In the publication, the PC also performs the operations (document reading start and various kinds of settings) of the image forming apparatus.
For the image forming apparatus, an extension copy function (pseudo copy function) has been proposed. This function processes an extensional copy function, which cannot be implemented by the hardware resource of the image forming apparatus, using the resource of an external apparatus such as a PC. The operation of this function can be done via the operation unit of the image forming apparatus. Hence, a scan driver program for controlling the document reading function of the image forming apparatus and a print driver program for controlling the print function are installed in the external apparatus. Upon receiving a copy start instruction from the user, the image forming apparatus notifies the external apparatus of the instruction. The external apparatus executes document reading, various kinds of image processing, and printing in accordance with the driver programs. Although document reading and printing are performed by the image forming apparatus, various kinds of image processing are executed by the driver programs and the hardware resource of the external apparatus. Even if the capacity of a memory provided in the image forming apparatus is small, the extension function allows layout processing and sort processing of multiple pages to be implemented by storing image data in the memory of not the image forming apparatus but the external apparatus. In addition, only a minimum necessary image forming unit is provided in the image forming apparatus. Complex advanced image processing and color processing are executed in accordance with an image processing program installed in the external apparatus. This enables to attain high functionality while reducing the cost of the image forming apparatus.
However, the above-described conventional technique has the problems to be described below. For example, a case is assumed in relation to the extension copy function in which when the user wants to cancel the extension copy operation in midstream, document read data has already been transferred to the external apparatus at that point of time. In this case, upon receiving the cancel instruction after the processing in the external apparatus has progressed, the image forming apparatus receives print data from the external apparatus and executes printing in spite of the cancel instruction. This is because the image forming apparatus recognizes the job of the extension copy function distinctively as a scan job and a print job in fact, and individual job IDs are assigned to the jobs. In addition, since the user's extension copy operation is performed in the image forming apparatus, the cancel instruction is grasped by the image forming apparatus but not by the external apparatus.
It is therefore necessary to send the cancel instruction to the external apparatus which receives document read data and executes processing. However, even if the image forming apparatus notifies the external apparatus of the cancel instruction, the already transferred document read data may remain in the external apparatus. This poses a problem from the viewpoint of both security and performance of the external apparatus.